Re: [v4,12/13] drm/fbdev-generic: Implement dedicated fbdev I/O helpers

[Thomas Zimmermann <tzimmermann@suse.de>]

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Hi

Am 24.05.23 um 22:23 schrieb Sui Jingfeng:
> Tested-by: Sui Jingfeng <suijingfeng@loongson.cn>
> 
> 
> This version works fine, I have tested it On LoongArch with 
> drm/loongson(v14) as it is most handy for me.
> 
> Also because it using fbdev-generic. fbdev of IGT report no error. Then 
> I run fbtest from geert[1],
> 
> 
> Before apply your patch:
> 
> 
> Benchmarking... 10x10 squares: 468.39 Mpixels/s
> Benchmarking... 20x20 squares: 985.02 Mpixels/s
> Benchmarking... 50x50 squares: 2247.22 Mpixels/s
> Benchmarking... 100x100 squares: 2242.30 Mpixels/s
> Benchmarking... 200x200 squares: 2883.18 Mpixels/s
> Benchmarking... 500x500 squares: 3642.18 Mpixels/s
> Benchmarking... 1000x1000 squares: 3992.77 Mpixels/s
> Benchmarking... R5 circles: 261.90 Mpixels/s
> Benchmarking... R10 circles: 596.27 Mpixels/s
> Benchmarking... R25 circles: 1513.96 Mpixels/s
> Benchmarking... R50 circles: 1965.07 Mpixels/s
> Benchmarking... R100 circles: 2470.75 Mpixels/s
> Benchmarking... R250 circles: 3288.00 Mpixels/s
> Benchmarking... R500 circles: 3705.66 Mpixels/s
> 
> 
> After apply your patch:
> 
> 
> Benchmarking... 10x10 squares: 477.04 Mpixels/s
> Benchmarking... 20x20 squares: 1021.07 Mpixels/s
> Benchmarking... 50x50 squares: 2315.70 Mpixels/s
> Benchmarking... 100x100 squares: 2267.69 Mpixels/s
> Benchmarking... 200x200 squares: 3006.28 Mpixels/s
> Benchmarking... 500x500 squares: 3761.44 Mpixels/s
> Benchmarking... 1000x1000 squares: 4112.49 Mpixels/s
> Benchmarking... R5 circles: 269.19 Mpixels/s
> Benchmarking... R10 circles: 620.77 Mpixels/s
> Benchmarking... R25 circles: 1559.02 Mpixels/s
> Benchmarking... R50 circles: 2027.36 Mpixels/s
> Benchmarking... R100 circles: 2574.42 Mpixels/s
> Benchmarking... R250 circles: 3363.28 Mpixels/s
> Benchmarking... R500 circles: 3815.51 Mpixels/s
> 
> 
> It seems that this bring a little bit performance gain.

Thanks for testing. I can't really tell why the code is now faster. All 
the patch really does is to eliminate an intermediate cross-module 
function call and the pointer derefs.  This, apparently, already has an 
impact.

Best regards
Thomas

> 
> Directly operate on video RAM is slower than have a shadow in system RAM.
> 
> I also test this patch in intel i3-8100 @ 3.6Ghz, the results show that 
> i915 is a bit slower.
> 
> Because it operate directly on device memory.
> 
> 
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/geert/fbtest.git
> 
> 
> On 2023/5/24 17:21, Thomas Zimmermann wrote:
>> Implement dedicated fbdev helpers for framebuffer I/O instead
>> of using DRM's helpers. Use an fbdev generator macro for
>> deferred I/O to create the callbacks. Fbdev-generic was the
>> only caller of the DRM helpers, so remove them from the helper
>> module.
>>
>> v4:
>>     * generate deferred-I/O helpers
>>     * use initializer macros for fb_ops
>> v2:
>>     * use FB_SYS_HELPERS_DEFERRED option
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
>> ---
>>   drivers/gpu/drm/Kconfig             |   6 +-
>>   drivers/gpu/drm/drm_fb_helper.c     | 107 ----------------------------
>>   drivers/gpu/drm/drm_fbdev_generic.c |  11 ++-
>>   include/drm/drm_fb_helper.h         |  41 -----------
>>   4 files changed, 6 insertions(+), 159 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
>> index 77fb10ddd8a2..92a782827b7b 100644
>> --- a/drivers/gpu/drm/Kconfig
>> +++ b/drivers/gpu/drm/Kconfig
>> @@ -95,6 +95,7 @@ config DRM_KUNIT_TEST
>>   config DRM_KMS_HELPER
>>       tristate
>>       depends on DRM
>> +    select FB_SYS_HELPERS_DEFERRED if DRM_FBDEV_EMULATION
>>       help
>>         CRTC helpers for KMS drivers.
>> @@ -135,11 +136,6 @@ config DRM_FBDEV_EMULATION
>>       select FB_CFB_FILLRECT
>>       select FB_CFB_COPYAREA
>>       select FB_CFB_IMAGEBLIT
>> -    select FB_DEFERRED_IO
>> -    select FB_SYS_FOPS
>> -    select FB_SYS_FILLRECT
>> -    select FB_SYS_COPYAREA
>> -    select FB_SYS_IMAGEBLIT
>>       select FRAMEBUFFER_CONSOLE if !EXPERT
>>       select FRAMEBUFFER_CONSOLE_DETECT_PRIMARY if FRAMEBUFFER_CONSOLE
>>       default y
>> diff --git a/drivers/gpu/drm/drm_fb_helper.c 
>> b/drivers/gpu/drm/drm_fb_helper.c
>> index cb03099fd2e3..bab6b252f02a 100644
>> --- a/drivers/gpu/drm/drm_fb_helper.c
>> +++ b/drivers/gpu/drm/drm_fb_helper.c
>> @@ -736,113 +736,6 @@ void drm_fb_helper_deferred_io(struct fb_info 
>> *info, struct list_head *pagerefli
>>   }
>>   EXPORT_SYMBOL(drm_fb_helper_deferred_io);
>> -/**
>> - * drm_fb_helper_sys_read - Implements struct &fb_ops.fb_read for 
>> system memory
>> - * @info: fb_info struct pointer
>> - * @buf: userspace buffer to read from framebuffer memory
>> - * @count: number of bytes to read from framebuffer memory
>> - * @ppos: read offset within framebuffer memory
>> - *
>> - * Returns:
>> - * The number of bytes read on success, or an error code otherwise.
>> - */
>> -ssize_t drm_fb_helper_sys_read(struct fb_info *info, char __user *buf,
>> -                   size_t count, loff_t *ppos)
>> -{
>> -    return fb_sys_read(info, buf, count, ppos);
>> -}
>> -EXPORT_SYMBOL(drm_fb_helper_sys_read);
>> -
>> -/**
>> - * drm_fb_helper_sys_write - Implements struct &fb_ops.fb_write for 
>> system memory
>> - * @info: fb_info struct pointer
>> - * @buf: userspace buffer to write to framebuffer memory
>> - * @count: number of bytes to write to framebuffer memory
>> - * @ppos: write offset within framebuffer memory
>> - *
>> - * Returns:
>> - * The number of bytes written on success, or an error code otherwise.
>> - */
>> -ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char 
>> __user *buf,
>> -                size_t count, loff_t *ppos)
>> -{
>> -    struct drm_fb_helper *helper = info->par;
>> -    loff_t pos = *ppos;
>> -    ssize_t ret;
>> -    struct drm_rect damage_area;
>> -
>> -    ret = fb_sys_write(info, buf, count, ppos);
>> -    if (ret <= 0)
>> -        return ret;
>> -
>> -    if (helper->funcs->fb_dirty) {
>> -        drm_fb_helper_memory_range_to_clip(info, pos, ret, 
>> &damage_area);
>> -        drm_fb_helper_damage(helper, damage_area.x1, damage_area.y1,
>> -                     drm_rect_width(&damage_area),
>> -                     drm_rect_height(&damage_area));
>> -    }
>> -
>> -    return ret;
>> -}
>> -EXPORT_SYMBOL(drm_fb_helper_sys_write);
>> -
>> -/**
>> - * drm_fb_helper_sys_fillrect - wrapper around sys_fillrect
>> - * @info: fbdev registered by the helper
>> - * @rect: info about rectangle to fill
>> - *
>> - * A wrapper around sys_fillrect implemented by fbdev core
>> - */
>> -void drm_fb_helper_sys_fillrect(struct fb_info *info,
>> -                const struct fb_fillrect *rect)
>> -{
>> -    struct drm_fb_helper *helper = info->par;
>> -
>> -    sys_fillrect(info, rect);
>> -
>> -    if (helper->funcs->fb_dirty)
>> -        drm_fb_helper_damage(helper, rect->dx, rect->dy, rect->width, 
>> rect->height);
>> -}
>> -EXPORT_SYMBOL(drm_fb_helper_sys_fillrect);
>> -
>> -/**
>> - * drm_fb_helper_sys_copyarea - wrapper around sys_copyarea
>> - * @info: fbdev registered by the helper
>> - * @area: info about area to copy
>> - *
>> - * A wrapper around sys_copyarea implemented by fbdev core
>> - */
>> -void drm_fb_helper_sys_copyarea(struct fb_info *info,
>> -                const struct fb_copyarea *area)
>> -{
>> -    struct drm_fb_helper *helper = info->par;
>> -
>> -    sys_copyarea(info, area);
>> -
>> -    if (helper->funcs->fb_dirty)
>> -        drm_fb_helper_damage(helper, area->dx, area->dy, area->width, 
>> area->height);
>> -}
>> -EXPORT_SYMBOL(drm_fb_helper_sys_copyarea);
>> -
>> -/**
>> - * drm_fb_helper_sys_imageblit - wrapper around sys_imageblit
>> - * @info: fbdev registered by the helper
>> - * @image: info about image to blit
>> - *
>> - * A wrapper around sys_imageblit implemented by fbdev core
>> - */
>> -void drm_fb_helper_sys_imageblit(struct fb_info *info,
>> -                 const struct fb_image *image)
>> -{
>> -    struct drm_fb_helper *helper = info->par;
>> -
>> -    sys_imageblit(info, image);
>> -
>> -    if (helper->funcs->fb_dirty)
>> -        drm_fb_helper_damage(helper, image->dx, image->dy, 
>> image->width, image->height);
>> -}
>> -EXPORT_SYMBOL(drm_fb_helper_sys_imageblit);
>> -
>>   /**
>>    * drm_fb_helper_cfb_read - Implements struct &fb_ops.fb_read for 
>> I/O memory
>>    * @info: fb_info struct pointer
>> diff --git a/drivers/gpu/drm/drm_fbdev_generic.c 
>> b/drivers/gpu/drm/drm_fbdev_generic.c
>> index 8e5148bf40bb..98ae703848a0 100644
>> --- a/drivers/gpu/drm/drm_fbdev_generic.c
>> +++ b/drivers/gpu/drm/drm_fbdev_generic.c
>> @@ -34,6 +34,10 @@ static int drm_fbdev_generic_fb_release(struct 
>> fb_info *info, int user)
>>       return 0;
>>   }
>> +FB_GEN_DEFAULT_DEFERRED_SYS_OPS(drm_fbdev_generic,
>> +                drm_fb_helper_damage_range,
>> +                drm_fb_helper_damage_area);
>> +
>>   static void drm_fbdev_generic_fb_destroy(struct fb_info *info)
>>   {
>>       struct drm_fb_helper *fb_helper = info->par;
>> @@ -56,13 +60,8 @@ static const struct fb_ops drm_fbdev_generic_fb_ops 
>> = {
>>       .owner        = THIS_MODULE,
>>       .fb_open    = drm_fbdev_generic_fb_open,
>>       .fb_release    = drm_fbdev_generic_fb_release,
>> -    .fb_read    = drm_fb_helper_sys_read,
>> -    .fb_write    = drm_fb_helper_sys_write,
>> +    FB_DEFAULT_DEFERRED_OPS(drm_fbdev_generic),
>>       DRM_FB_HELPER_DEFAULT_OPS,
>> -    .fb_fillrect    = drm_fb_helper_sys_fillrect,
>> -    .fb_copyarea    = drm_fb_helper_sys_copyarea,
>> -    .fb_imageblit    = drm_fb_helper_sys_imageblit,
>> -    .fb_mmap    = fb_deferred_io_mmap,
>>       .fb_destroy    = drm_fbdev_generic_fb_destroy,
>>   };
>> diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
>> index 7d5804882be7..b50fd0c0b713 100644
>> --- a/include/drm/drm_fb_helper.h
>> +++ b/include/drm/drm_fb_helper.h
>> @@ -258,18 +258,6 @@ void drm_fb_helper_damage_area(struct fb_info 
>> *info, u32 x, u32 y, u32 width, u3
>>   void drm_fb_helper_deferred_io(struct fb_info *info, struct 
>> list_head *pagereflist);
>> -ssize_t drm_fb_helper_sys_read(struct fb_info *info, char __user *buf,
>> -                   size_t count, loff_t *ppos);
>> -ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char 
>> __user *buf,
>> -                size_t count, loff_t *ppos);
>> -
>> -void drm_fb_helper_sys_fillrect(struct fb_info *info,
>> -                const struct fb_fillrect *rect);
>> -void drm_fb_helper_sys_copyarea(struct fb_info *info,
>> -                const struct fb_copyarea *area);
>> -void drm_fb_helper_sys_imageblit(struct fb_info *info,
>> -                 const struct fb_image *image);
>> -
>>   ssize_t drm_fb_helper_cfb_read(struct fb_info *info, char __user *buf,
>>                      size_t count, loff_t *ppos);
>>   ssize_t drm_fb_helper_cfb_write(struct fb_info *info, const char 
>> __user *buf,
>> @@ -397,35 +385,6 @@ static inline int drm_fb_helper_defio_init(struct 
>> drm_fb_helper *fb_helper)
>>       return -ENODEV;
>>   }
>> -static inline ssize_t drm_fb_helper_sys_read(struct fb_info *info,
>> -                         char __user *buf, size_t count,
>> -                         loff_t *ppos)
>> -{
>> -    return -ENODEV;
>> -}
>> -
>> -static inline ssize_t drm_fb_helper_sys_write(struct fb_info *info,
>> -                          const char __user *buf,
>> -                          size_t count, loff_t *ppos)
>> -{
>> -    return -ENODEV;
>> -}
>> -
>> -static inline void drm_fb_helper_sys_fillrect(struct fb_info *info,
>> -                          const struct fb_fillrect *rect)
>> -{
>> -}
>> -
>> -static inline void drm_fb_helper_sys_copyarea(struct fb_info *info,
>> -                          const struct fb_copyarea *area)
>> -{
>> -}
>> -
>> -static inline void drm_fb_helper_sys_imageblit(struct fb_info *info,
>> -                           const struct fb_image *image)
>> -{
>> -}
>> -
>>   static inline ssize_t drm_fb_helper_cfb_read(struct fb_info *info, 
>> char __user *buf,
>>                            size_t count, loff_t *ppos)
>>   {

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

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